1. Field of the Invention
The present invention relates generally to wire line extensometers of the type used to measure movement of a sloped wall in an open pit mine, dump, or the like, and more particularly to a slope monitoring device adapted to operate for extended periods of time without manual intervention.
2. Description of the Prior Art
Within the field of open pit mining, the use of wire line extensometers is well known for detecting and monitoring movement of sloped walls of open pit mines or dumps in advance of the collapse of the wall. Such wire line extensometers typically include a cable anchored at one end to the sloped wall and secured at the opposing end to a pointer and a free-hanging counterweight. Periodically, a mine employee must drive to the site of the extensometer, visually observe the status of the pointer, record the result, and compare the result to the reading observed on the prior day in order to detect any shift in the sloped wall. The need for the mine employee to periodically visit the site of the extensometer to record such measurements is a nuisance, particularly since there may be several extensometers scattered throughout the mine, each of which must be regularly visited.
Further, wire line extensometers that are presently used in open pit mining operations must be manually reset frequently in order to keep the pointer within the range of the measuring scale. Continued movement of the sloped wall ultimately pulls the pointer off the scale. In such instances, the mine employee must reset the pointer, as by lengthening the cable, in order to move the pointer back onto the measuring scale.
Wire line extensometers that are presently used today are typically observed once per day or more often. While movement of a sloped wall is usually a very slow process, the rate of wall movement often accelerates prior to a collapse. Unfortunately, it is difficult to detect such accelerated movement when observations are made only once per day.
Changes in wire line extensometer measurements may sometimes be caused by changes in temperature rather than by significant movement of the sloped wall. Such wire line extensometers typically use a steel cable which tends to expand or contract depending upon the ambient temperature. Those wire line extensometers currently in use are unable to distinguish between measurement changes due to actual wall movement as compared with measurement changes due to varying ambient temperature.
Wire line extensometers must often be moved from one point to another in an open pit mining operation. Moreover, such devices must be of rugged construction to survive in a mining environment.
Accordingly, it is an object of the present invention to provide a slope monitoring device for detecting and measuring movement of a sloped wall in an open pit mine, dump, or the like, which slope monitoring device avoids the need for daily inspections by a mine employee at the site of such slope monitoring device.
It is another object of the present invention to provide such a slope monitoring device which can operate for extended periods without requiring a user to manually reset the device due to movement of the sloped wall.
It is still another object of the present invention to provide such a slope monitoring device which periodically and automatically provides status information regarding sloped wall movement to a remote location.
A further object of the present invention is to provide such a slope monitoring device responsive to ambient temperature conditions as might cause relative expansion or contraction of the extensometer cable.
A still further object of the present invention is to provide such a slope monitoring device which automatically signals the user when on-site maintenance is required.
Yet another object of the present invention is to provide such a slope monitoring device which is relatively inexpensive to manufacture, easily portable, simple to install, and rugged enough to withstand the open pit mining environment.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.